diff --git a/ext/mri/ow-crypt.h b/ext/mri/ow-crypt.h
index 2e48794..d792ae0 100644
--- a/ext/mri/ow-crypt.h
+++ b/ext/mri/ow-crypt.h
@@ -24,7 +24,6 @@
 
 #ifndef __SKIP_GNU
 extern char *crypt(__const char *key, __const char *setting);
-extern char *crypt_r(__const char *key, __const char *setting, void *data);
 #endif
 
 #ifndef __SKIP_OW
diff --git a/ext/mri/wrapper.c b/ext/mri/wrapper.c
index 1e49c90..ef45488 100644
--- a/ext/mri/wrapper.c
+++ b/ext/mri/wrapper.c
@@ -176,13 +176,6 @@ char *crypt_ra(const char *key, const char *setting,
 	return _crypt_blowfish_rn(key, setting, (char *)*data, *size);
 }
 
-char *crypt_r(const char *key, const char *setting, void *data)
-{
-	return _crypt_retval_magic(
-		crypt_rn(key, setting, data, CRYPT_OUTPUT_SIZE),
-		setting, (char *)data, CRYPT_OUTPUT_SIZE);
-}
-
 char *crypt(const char *key, const char *setting)
 {
 	static char output[CRYPT_OUTPUT_SIZE];